Cigarette filter and method of manufacture



July 30, 1968 c. A. ELLIS 3,394,707

CIGARETTE FILTER AND METHOD OF MANUFACTURE Filed Oct. 8, 1964 37 7INVENTOR.

CHARLES A. ELLIS United States Patent 3,394,707 CIGARETTE FILTER ANDMETHOD OF MANUFACTURE Charles A. Ellis, Point Road, Marion, Mass. 02738Filed Oct. 8, 1964, Ser. No. 402,422 Claims. (Cl. 131-105) ABSTRACT OFTHE DISCLOSURE An improvement in cigarette filter consisting of dieformed cup shaped elements, the bottoms multiplyperforated by narrowtapered slots, the sides shaped to provide controlled nesting andperipheral sealing in a rod like assembly of elements adapted tohandling for machine assembly in cigarettes.

This invention relates to improvements in filter devices for filter-tipcigarettes in which the filter is an integral portion of the cigarette,and has particular reference to the use of interlocking cup shapedelements for improvement of the filtering action for removal of tars andvapors from the raw cigarette smoke.

One object of this invention is to provide means for elimination ofheavy tars and vapors before they reach the surface active filterelement in order that the latter may trap the lighter and move volatilecombustion products in a more effective manner.

Another object is to provide in a filter system a section of reducedarea of such a shape as to promote a high degree of turbulence in thesmoke stream passing therethrough whereby changes in vapor velocity willaid in condensation of vaporized materials.

Another object is to provide means for minimizing the pressure dropalong a filamentary type of filter in order that channeling effects dueto non-uniformity of sectional resistance may be reduced to a minimumand maximum filter surface exposure attained.

Still another object is to provide for the incorporation of suchmetallic elements in the cigarette in a manner adapted to the automatedmass production methods of the cigarette industry.

Other objects and advantages of the invention will become apparent fromthe following description taken in connection with the accompanyingdrawings in which:

FIG. 1 is a sectional view of a filter-tip cigarette taken along itslongitudinal axis, embodying one form of the invention;

FIG. 2 is a longitudinal sectional view of a single cup element;

FIG. 3 is an elevation view of the cup element of FIG. 2 as seen lookingtoward the bottom of the cup from the outside;

FIG. 4 is an enlarged fragmentary view of a portion of the base of a cupillustrating a detail of a number of preferred types of perforation;

FIG. 5 shows a continuous length of interlocking cup elements assembledfor ease of handling in automatic cigarette making machines;

FIG. 6 illustrates the manner of separation of the element of FIG. 1from the continuous stick form of FIG. 5.

FIG. 7 shows a longitudinal section of an assembly of three interlockingcup elements as prepared for unit loading in cigarette making machines.

At the present time much attention is being given to improving thefilter efficiency of filter-tip cigarettes, particularly since thepublic health report associating high rates of lung cancer with heavycigarette smoking habits. While no claim is made that the subjectinvention will in any way affect lung cancer rate it can be unequivocal-See ly stated that the combination of the multiple interlocking cupelement of this invention with any of the presently used filamentarysurface active filters does remarkably improve their filtering capacity.

The improvement in filter action is brought about primarily by acombination of a number of different effects. The interlocking dieformed metallic cup elements of themselves serve to trap and containtars and large amounts of moisture condensed from the combustionproducts. This effects a two-fold improvement in action of thefilamentary filter element; mass fiow through the filter is reduced andremoval of water and tar leaves the filter free to trap volatilehydrocarbons. Another effect is limitation of total mass flow throughthe perforations to a critical amount. This means that excessive drawingof air through the cigarette is prevented and as a result the maximumburning temperature is considerably reduced. High burning temperaturesare known to produce more injurious combustion products than thoseproduced at lower temperature. Still another effect is the reduction inpressure drop along the length of the filamentary filter element withthe result that nonuniformity of filamentary packing is less critical asto channeling potential and more uniform exposure of the filter surfaceresults.

Referring more particularly to the drawings in which like characters ofreference designate like parts throughout the several views; in FIG. 1,1' generally indicates a filter-tip cigarette embodying this invention.A tobacco column 10 is enclosed in a paper wapper 13. Attached at oneend of the wrapper is a tubular mouthpiece 12 of moisture resistantpaper or other suitable material. Enclosed within the tubular mouthpieceadjacent the tobacco column is a multiple interlocking cup filterassembly generally indicated at 3' together with a filamentary type offilter element 11 at the outer extremity thereof. The assembly 3 iscomprised of a number of interlocking cup elements, the sides of thecups preferably of stepped form with shoulder at 17 and so proportionedthat the outer surface of small diameter 15 is a tight fit in the innersurface of large diameter 14 of another cup. With good size control ithas been found unnecessary to use cementing material between thesesurfaces but cementing may be required where such control is inadequateto provide a secure fit. The outer surface of the large diameter portionof the cups is preferably adhered to the tube material as it is rolledso as to provide a positive seal around the periphery of the cups. Eachcup bottom 16 is perforated in a completely random pattern by a numberof perforations 18. It is important that the total area of suchperforations be of the order of from one to three percent of the tobaccocolumn cross section. It is also important that the perforations be verysmall in one dimension. Expressed in another way it is important thatthe ratio of hole edge length to hole area be maximized. In a circlethis ratio is at a minimum, in an infinitely narrow simple slit it is ata maximum. In our application the slit edge is effective as a weir forthe combusted gases and, to the extent of gas exposure, acts as a highconductive cooling means for reducing gas temperature to aid incondensation. However, the requirement for motion to produce valveaction, as explained more fully below, provides a practical limit to theratio beyond which some benefits of the multi-functional aspects ofthese perforations would be sacrificed. various form of suchperforations are clearly illustrated in FIG. 4. The Y-shaped perforation18 has three such tabs, the cross-shaped perforation 19 has four tabsand the H-shaped perforation 20 has two tabs. These tabs are slightlyflexible and project outwardly from the bottom surface of the cups. 'Intheir assembled position within a cigarette the tabs point up-stream ofthe air flow during use. If the airstream is normal, that due to thenormal average smoker, the resistance to flow is not enough tosignificantly load these tabs to cause bending. If the air stream isexcessive, such as that due to impulsive inhalation, the resistance tofiow being somewhat higher will cause bending of the tabs and actualreduction of air flow. The purpose here is to limit the air stream togive a degree of control to the temperature of combustion of thetobacco. The impulsive inhaler not only takes a great deal of smoke intohis lungs normally but much of it is from high temperature combustionproducts. Another reason for having the perforations in the form shownis that the actual openings have the shape of a tapered slot. This formof perforation produces very pronounced turbulence on the exit side ofthe sealing wall, much more than from a regular or round hole forexample, with significant pressure changes in short time periods whichare conducive to good separation of the moisture and heavy hydrocarbons.A further reason for selecting this form of perforation is the very longedge compared with area so that the intimate contact with the combustionproducts results in a maximum cooling effect upon the gas and vaporpassing through, the wide tabs serving as highly conductive pathways forthe dissipation of absorbed heat away from the openings.

In order to promote the condensation of the heavy components by themetallic element the greatest pressure drop should be across thatelement since the pressure changes through the element will determinethe turbulence in the smoke stream as it passes through the slots.Physical nonuniformity of packing in the filamentary portion produceshole effects which modify the exposure to surface action inversely withthe degree of openness of the holes at constant pressure. However atgreater pressure drop from end to end of the filaments the mass flowthrough the low resistance holes increases faster than the pressurechange and the result is less filter exposure. Thus it is highlydesirable to proportion the filter resistances with these principles inmind. High resistance metallic and low resistance filamentary portionsare optimal within the permissible total resistance.

In the practical application of the interlocked cup elements to theproduction of filter cigarettes the die formed cups may be assembled insticks of standard or continuous length as best shown in FIG. 5. Thesticks would then be introduced into a cigarette-forming machine withautomatic means for feeding and cutting. Cutting could be convenientlyat any integral multiple of a half cup length. FIG. 6 shows how a cut at8-8 and another at 99 separated by three half-lengths produces a filterunit comprising three perforated walls similar to that shown at 3' inassembled position in the cigarette of FIG. I. The small diameterhalf-portion 22 fits within and reinforces large diameter portion of thecup on the left and the large diameter half-poriton 21 fits over andreinforces the small diameter portion of the right hand cup. The threesections of large diameter, being alike, define an outer cylindricalsurface suitable for assembly with and adherence to the moisture-proofouter lip-contacting portion of the cigarette. In this form it is easyto handle and to assemble with the filamentary or fibrous element 11.Another form of filter unit suited to another type of cigarette-makingmachine is made up of a unit of three interlocking cups as shown inFIGURE 7. These may be formed, punched and stacked in a conventionalcut-and-carry type of die forming machine closely adjacent to thecigarette rolling machine and passed to the latter as a unit assemblyfor incorporation in a cigarette.

Cigarette-making machines are in general costly precision equipment. Inorder that the benefits of this invention may be made more easilyavailable commercially without extensive capital investment incompletely new machines I contemplate the construction of auxiliaryfilterforming machines as the major cost element. In one arrangement theunit filter comprising a multiple nested cu-p element would be formedand passed to the cigarette-making machine by a synchronized transfermechanism for incorporation in the cigarette. In a second arrangementthe filter cups would be continuously formed and nested by the newmachine equipment and fed in continuous form to the cigarette-makingmachine where filter units would be synchronously separated forincorporation in the cigarettes. A third arrangement contemplatescontinuous forming and nesting of cups in stick form with an additionaloperation of cutting to standard stick lengths. The sticks thus formedwould then be hopper fed into the cigarette-making machine with unitcutting phased into the cigarette assembly operation.

Cups of the form shown have been easily formed from .001 sheet aluminumfoil which is well suited for the purpose because of the high heatconductivity of the aluminum material and also because of its lightweight and inlert character. Even in such a thin section the cups areeasily and safely handled and when cemented in the tube give the lattersubstantial reinforcement. However, plastic cups are also satisfactory.

In laboratory work carried on in conjunction with this development itwas found that the filter unit 3' would, of itself, and when used alone,separate out quantities of tar and water from the smoke of tobacco. Todetermine what combustion products were passing through trials were runwith standard filter cigarettes, first as purchased, then with others ofthe same pack cut at the filter-tobacco interface and a metallicinterlocking cup unit interposed between the filter and tobacco. Inevery case the materials caught behind the auxiliary unit wereapproximately double those trapped in the filter of a standard assembly.Examination of the metallic units showed that they were still trappingboth tar and moisture in the same quantities as before. The eliminationof the easily-condensed low volatile products from the smoke streamincreased markedly the effectiveness of the surface active filter inremoval of the more highly volatile hydrocarbon products. About twentypercent of the production cigarettes showed uneven staining of thefilters, not always in the same areas, indicating a channeling effectdue to non-uniform fiber packing. None of the filters behind themetallic cup elements showed such channeling.

While I have described methods by which the objects and advantages ofthis invention may be realized I wish to point out that changes may bemade in the details of construction and arrangement of parts shown anddescribed without departing from the spirit of the invention. Therefore,it is to be understood that all of the matter set forth and shown in theaccompanying drawings is to be interpreted as illustrative and not in alimiting sense.

I claim:

1. In a filter-tip cigarette of the character described the combinationof auxiliary filter means comprising a plurality of identicalinterlocking metallic die formed cup elements, forming a substantiallyunitary structure the bottom wall only of each of said cups perforatedin random pattern with a plurality of narrow tapered slots, the saidslots having a total area per cup of not less than one percent nor morethan three percent of the area of the said bottom wall in order that theresistance of the cup elements shall be high relative to the resistanceof the filter as a whole; and the said slots having the ratio of edgelength to area of opening maximized to promote condensation by cooling;together with a surface active filter wholly external to said cupsabutting one end of said unitary structure; and a tobacco columnabutting the other end of the said unitary structure, all within atubular wrapper.

2. The article of claim 1 in which the edges of the said slots projectslightly outward of the plane of the bottom of said cup elements, theopposed edges of said slots adapted to elastic deformation toward saidplane and toward one another with the passage of smoke through theslots, the said deformation acting to significantly increase theresistance to the flow of smoke only during impulsive drawing upon thecigarette, and the elasticity of said edges sufiicient to return theedges to define substantially the original area of the slots uponcessation of such impulsive drawing.

3. The article of claim 1 in which the said cup elements are furthercharacterized by: peripheral wall surfaces coacting to form a first sealagainst the passage of smoke between such surfaces, together with thecircumferential grooves between the edges of the said cup elements andthe wall of the adjacent cup adapted to receive circumcferential areasof the inside surface of the tubular wrapper to form a second sealbetween said inside surface and the unitary structure taken as a whole.

4. As an article of manufacture an auxiliary filter means for cigarettescomprising the combination of a plurality of identical interlockingdie-formed metallic cup elements to form a substantially unitarystructure, the said structure adapted for assembly within a cigarette inabutting relation between a column of tobacco and a surface activefibrous filter, the bottom wall only of each of said cups perforated inrandom pattern with a plurality of narrow tapered slots, the said slotshaving a total area of not less than one percent nor more than threepercent of the area of said bottom wall, and the said slots having aratio of edge length to area of opening maximized, these conditionscombining to promote deposit of low volatile products of combustionwithin the auxiliary filter and to prevent wetting and channeling of thefibrous filter so that the said fibrous filter may more effectively trapthe more volatile combustion products when the said article is in usetherewith.

5. As an article of manufacture an auxiliary filter means for cigarettescomprising: the combination of a plurality of identical interlocking dieformed metallic cup elements to form a substantially unitary structureof rod-like form; the separation of a short substantially unitarysection of said structure to include a plurality of said cup elements toform a first filter element adapted for assembly within a cigarette inabutting relation between a column of tobacco and a fibrous secondfilter element; the bottom wall only of each of said cups perforated inrandom pattern with a plurality of narrow tapered slots, the said slotshaving a total area of not less than one percent nor more than threepercent of the area of said bottom wall, and the said slots having aratio of edge length to area of opening maximized to promotecondensation of the least volatile combustion products within the saidfirst filter element when in use and so assembled.

References Cited UNITED STATES PATENTS 267,070 11/1882 Franke 131-2103,064,657 11/ 1962 Sh'riner 13110.7 3,172,410 3/1965 Miller 13110.53,250,280 5/1966 Yow-Jiun-Hu 131-105 LUCIE H. LAUDENSLAGER, PrimaryExaminer.

